amend! Fix gpu.set_default_device rewriting.

Fix gpu.set_default_device rewriting to properly use the new call.
Smoke test included.

Author: pcf000

mlir/test/Conversion/GPUCommon/set-default-device.mlir

@@ -0,0 +1,10 @@
+// RUN: mlir-opt %s --gpu-to-llvm | FileCheck %s
+
+module attributes {gpu.container_module} {
+  // CHECK-LABEL: func @set_default_device
+  func.func @set_default_device(%arg0: i32) {
+    // CHECK: mgpuSetDefaultDevice
+    gpu.set_default_device %arg0
+    return
+  }
+}